semifixed

Semifixed is an adjective used to describe something that is neither fully fixed nor fully variable. The term appears in different disciplines, where its meaning is related but not identical across contexts. In economics and cost accounting, semifixed costs (often described as semi-fixed or step costs) are costs that remain constant within a certain level of activity but rise in discrete steps when activity crosses thresholds. This contrasts with fixed costs that do not change with activity and with variable costs that change proportionally to output. Semifixed costs are commonly analyzed using step-variable or relevant-range concepts to determine cost behavior and break-even points. They are sometimes treated as a subset of mixed costs or as a distinct category reflecting the step-like nature of cost changes. Examples include supervisory salaries or facility maintenance charges that stay the same over a range of production and then increase when capacity is expanded.

In linguistics and language studies, semifixed expressions refer to collocations or idiomatic phrases that are largely fixed but permit limited variation. They are intermediate between fully fixed expressions and freely productive combinations. A semifixed expression may allow substitution of certain content words or adjustments for number, tense, or aspect while the core sequence or pre-determined syntax remains intact. The term is used variably across literature and is not a universal label; some authors prefer semi-fixed collocation or semi-idiomatic expression depending on the analytic framework.

See also: fixed cost, variable cost, mixed cost, step cost, collocation, idiom.